JPH01192061A - Video floppy reproducing device - Google Patents

Abstract

PURPOSE:To simplify the constitution of a BPF without making it into a narrow band area when video signals FM-modulated and recorded on a recording medium with first and second different frequencies by providing first and second BPFs, envelope detection circuits, and sample - hold circuits, and comparing signals processed and held by first and second circuits with each other by a comparator. CONSTITUTION:At the time of regenerating the video signals FM-modulated with the first and second different frequencies on the recording medium in a video floppy reproducing device, the frequencies equivalent to first and second flyback sections of a reproduced FM signal (a) are separated at the first and second BPFs 1 and 2. The envelope components of the separated FM signal are detected at the first and second envelope detection circuits 3 and 4, and detected envelope signals are held at the sample and hold circuits 5 and 6 by the synchronizing signal of the video signal, and the sample and held signals are compared at the comparator 7, then, a regenerating signal is outputted to an output terminal 8.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a magnetic recording and reproducing apparatus, and more particularly to a video floppy reproducing apparatus that records and reproduces video signals on a rotating magnetic sheet.

BACKGROUND ART Conventionally, in magnetic recording and reproducing devices such as video tape recorders and video floppy devices, new recording methods aiming at higher image quality have been introduced in addition to the basic recording methods. For example, in video tape recorders, there was a method that enabled a significant improvement in resolution by shifting to an FM variable frequency short wavelength recording section.In the past, there were two recording methods for magnetic tapes, and when playing back, the video signal was circuit.

It is necessary to switch.

A new recording method has been desired for video floppy recording/playback devices to achieve higher image quality.

FIG. 3 is a frequency characteristic diagram showing the above-mentioned more advanced recording method.

The video signal recorded as shown in Figure 3 consists of a first FM modulation signal of 7.6 to 9 degrees and a second FM modulation signal of 6 to 7.5 degrees between the synchronization signal and the white peak on the magnetic sheet. (not shown).

Conventionally, when attempting to introduce such a plurality of recording methods, it is necessary to switch the reproduced video signal circuit according to the recording method during reproduction to correspond to recording.

Furthermore, for video floppies that do not have a physical identification device, it is necessary to select the recording method from the playback signal.

Problems to be Solved by the Invention However, in the above configuration, the FM modulation frequency becomes a short wavelength recording and the reproduced signal amplitude decreases.
It was necessary to set the M modulation frequencies closely.

Therefore, with commonly used bandpass filters, FM
There was a problem in that the recording method could not be determined based on the presence or absence of a carrier.

Means for Solving the Problems In order to achieve the above-mentioned object, the present invention has the following objectives: When reproducing a video signal FM-modulated and recorded on a recording medium at first and second different frequencies, the reproduced first and second FM signals are first and second bandpass filters that separate frequencies corresponding to the retrace section of the FM signals; first and second envelope detection circuits that detect envelope components of the FM signals separated by the respective bandpass filters; first and second sample/hold circuits that sample/hold the envelope signal detected by the envelope detection circuit using a synchronization signal of the video signal; and a comparator that compares the first and second sample/hold signals. It has a well-equipped structure.

Effect of the Invention With the above-described configuration, the present invention uses a band-pass filter having a different frequency band to convert the reproduced FM signal during reproduction of a video signal that has been FM-modulated and recorded on a recording medium at first and second different frequencies into a video signal. The FM signal frequency corresponding to the flyback section is separated, and the envelope detector detects the envelope signal, which is the amplitude component, of the separated FM signal.

Since the reproduced Flvl signal has a different FM modulation frequency depending on the recording method, one envelope signal has a larger amplitude than the other envelope signal due to the frequency difference.

Further, the envelope signal is sampled/held using the synchronization signal of the video signal and temporally separated into envelope signals of only the retrace section of the video signal.

The envelope signal is converted into a binary signal of high level and low level by comparing voltages with a comparator.

As a result, this binary signal corresponds to the selection of the recording method.

Example An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, the FM signal a reproduced during playback is input to a band pass filter 1 whose center frequency is approximately 8-, which corresponds to the synchronization signal of the video signal, and a band pass filter 2 whose center frequency is approximately 61k, respectively. frequency separated.

The FM signal S separated by the bandpass filter 1 and the FM signal b' separated by the bandpass filter 2 are subjected to amplitude detection by envelope detectors 3 and 4, respectively, to obtain envelope signals C and C'.

The envelope signals C and C' are sampled and held by the sample/hold circuits 6 and 6, which sample and hold the video signal d using the synchronization signal e, to obtain sample and hold signals f and iI having amplitudes only in the period of the synchronization signal e.

The voltage comparator 7 compares the voltages of the input sample and hold signals f and f', and determines whether the amplitudes of the sample and hold signals f and f' are f ) f/ or f(
For example, 5V or Ov is outputted to the output terminal 8 by f'.

As mentioned above, since the FM modulation frequency of the reproduced FM signal differs depending on the recording method, one envelope signal has a larger amplitude than the other envelope signal due to the difference in the tube wave number, and this magnitude relationship It is possible to easily detect which recording method has been selected by the binary signal indicating the .

Effects of the Invention According to the present invention, by separating the reproduced FM signal in frequency and time using a band-pass filter and a sample/hold circuit, a recording method can be selected even if the FM modulation frequencies are close to each other. It is not necessary to configure the bandpass filter to have a narrow band, and it can be provided at low cost.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a video floppy playback device according to an embodiment of the present invention, FIG. 2 is a waveform diagram for explaining FIG. 1, and FIG. FIG. 2 is a frequency characteristic diagram of an FM signal. 1.2...Band pass filter, 3,4...
...Envelope detector, 6,6...Sample/hold circuit, 7...Comparator. Name of agent: Patent attorney Toshio Nakao and 1 other person 2nd
Figure 3

Claims (1)

[Claims] When reproducing a video signal FM-modulated and recorded on a recording medium at first and second different frequencies, first and second FM signals are configured to separate frequencies corresponding to blanking intervals of the reproduced first and second FM signals. a second bandpass filter, first and second envelope detection circuits that detect envelope components of the FM signal separated by the bandpass filters, and convert the envelope signals detected by the envelope detection circuits into the video signal. 1. A video floppy playback device comprising: first and second sample/hold circuits that sample/hold using a synchronizing signal; and a comparator that compares the first and second sample/hold signals.